Thursday, October 28, 2010

No Nuts, No Problem: Squirrels Harvest Maple Syrup

"It's nice to get models and think about why some [animals store food] and others don't," Heinrich said. "Bears don't have to. They get so fat and lazy, they turn on the hibernation hormone and their appetite is suppressed and they're fine."

Harsh winter weather can be a hardship for any creature. But naturalists say the amount of mastnuts, acorns, and the likethat drops on the forest floor in the fall is a key indicator of how well food-storing animals will survive come winter.

The abundance of mast is cyclical and related to reproduction strategies, according to Heinrich. If only one tree produced a bunch of nuts one year, critters would eat them all, and the tree would stand little chance at producing offspring.

Therefore trees in any given region collectively alternate between years of producing a lot of mast or very little. In years when they produce a lot, there is sufficient food for all the critters, and plenty of the nuts and acorns will be left over to take root.

"But sometimes there's not enough mast, and no matter what [the animals] store, it's insufficient to get them through winter," Serrao, the Pennsylvania naturalist, said. "They have to look for other means of energy, and that's probably when the red squirrels do more of the sugar scraping."

Hibernating black bears also depend on mast in the autumn to fatten up for their winters' slumber. When there's not much mast around, they go into hibernation early instead of wasting their energy looking for nuts and acorns that aren't there, Serrao said.

While a few animals will starve to death when food supplies are low, the species will survive. "Winter may be one of the chief conditions that limit the populations of some of the animals," Serrao said. "But never, except in extreme circumstances like a heavy winter snow, never do they have extensive mortality."